1. Field of the Invention
The present invention relates to printing apparatuses, media detection apparatuses, media detection methods, measurement methods, computer-readable storage media, and printing systems.
2. Description of the Related Art
When carrying out printing on a medium such as paper, various printing apparatuses such as inkjet printers execute printing by, for example, supplying the medium from a paper-supply portion and ejecting ink onto the medium while carrying the supplied medium in a predetermined direction. In such printing apparatuses, a sensor is provided (see JP 2003-63080A for example) to confirm the presence of the medium so that a printing operation is not executed when a medium has not been supplied from the paper-supply portion.
The sensor is arranged at the paper-supply portion side of the printing apparatus and confirms whether or not the medium has been supplied to a predetermined position. Ordinarily, a contact-type sensor that detects the medium when contact is made with the medium is used for this sensor. The contact-type sensor is provided with a lever, for example, that contacts the medium and, when the lever rotates due to contact with the medium, outputs a signal indicating that a medium has been detected. Furthermore, when the lever moves away from the medium and returns to its original position, the sensor outputs a signal indicating that the medium is not being detected.
However, contact-type sensors provided with such a lever or the like have the following problems. Namely, a slight time difference occurs from when the medium and the sensor enter a non-contact state until the sensor outputs a signal indicating that the medium is not being detected, and therefore it is extremely difficult to accurately obtain the timing at which the sensor and the medium actually entered a non-contact state. In particular, since the respective time differences are different for respective sensors even for the same type of sensor due to the installed position of the sensor, manufacturing error, and the like, it is extremely difficult to estimate the correct timing at which the sensor and the medium enter a non-contact state.
Being unable to obtain the timing at which the sensor and the medium entered a non-contact state has caused the following inconveniences. Namely, since the timing at which the medium and the sensor entered a non-contact state is not known when attempting to detect the position of a rear end portion of the medium after the medium and the sensor have gone into a non-contact state, it has not been possible to determine the correct position of the medium. For this reason, it has been extremely difficult to determine the position of the rear end portion of the medium when, for example, carrying the medium slowly so as to ensure the rear end portion does not rise up when the rear end portion of the medium passes the carry rollers, or when executing “borderless printing” in which printing is carried out to the very end of the rear end portion of the medium. For this reason, inconveniences have occurred, such as extra time being taken in processing, which tends to reduce printing speed, and extra ink having to be ejected.